YEAR OF THE LASER

摘要

This year is the 50th anniversary of the laser, a device used in applicationsrnfrom performing precise surgical procedures to measuring gravitationalrnwaves. In 1917, Albert Einstein proposed that a photon hitting an atomrnin a high energy state would cause the atom to release a second photonrnidentical in frequency and direction to the first. In the 1950s, scientistsrnsearched for a way to achieve this stimulated emission and amplify it sornthat a group of excited atoms would release photons in a chain reaction.rnIn 1959, American physicist Gordon Gould publicly used the term "lightrnamplification by sti mulated emission of radiation" for the first time. Arnyear later, scientists demonstrated the first working optical laser (left).